1. Technical Field
The present invention relates to a composition for conductive roller, a conductive roller, a charging unit, an image forming apparatus, a process cartridge, and a method of manufacturing a conductive roller.
2. Related Art
As the conductive roller that is installed into an image forming apparatus such as an electrophotographic apparatus, an electrostatic recording apparatus, or the like, typified by a copying machine, a printer, a facsimile machine, or the like, the electron conductive type conductive roller and the ion conductive type conductive roller, whose approaches of acquiring its electric resistance value are different, are known. Commonly the conductive roller has an elastic layer on an outer periphery of a conductive shaft body, and the elastic layer contains a rubber composition. In order to acquire a predetermined desired resistance value, in the electron conductive type conductive roller, the rubber composition is manufactured by mixing/dispersing conductive particles such as the carbon black, the metal oxide, or the like, for example, into the rubber material, or the like. At this time, the resultant resistance value depends greatly on a dispersed state of the conductive particles in the rubber composition.
Owing to the above circumstances, normally the ion conductive type conductive roller is mostly employed as the conductive roller that is installed into the image forming apparatus. As an example of the ion conductive type conductive roller, the roller whose elastic layer contains the rubber composition that consists of a copolymer of ethylene oxide and epichlorohydrin, a polymer such as an acrylonitrile-butadiene copolymer rubber, or the like may be listed. Since the rubber composition has a small variation in an electric resistance and a desired resistance value is obtained stably, the ion conductive type conductive roller is suitable for the image forming apparatus.
As an example of the epichlorohydrin rubber used in the conductive roller, a ternary copolymer (DECO) consisting of epichlorohydrin (ECH), ethylene oxide (EO), and allyl glycidyl ether (AGE) is listed. The ternary copolymer containing the epichlorohydrin rubber may be vulcanized by various sulfur-based vulcanizing agents. Since a vulcanization rate may be easily adjusted by changing its combination, various sulfur-based vulcanizing agents are excellent in workability. However, since the allyl glycidyl ether unit part, in which the vulcanization action is executed, of the ternary epichlorohydrin rubber is expensive, it is feared that a material cost is increased.